1. Field of the Invention
The present invention relates to an optical cloaking system, and in particular, to an optical cloaking system which can optically cloak/hide objects in the visible light spectrum such that the objects appear invisible, and which can be efficiently and practically manufactured using common optical materials in the form of prisms, lenses, mirrors, and the like to. Such optical cloaking system bends and/or compresses light such that, within the system, the light passes around a cloaked space in which an object is disposed, and a person viewing a larger space including the cloaked space will not see the object, but in certain embodiments will see a background behind the object in full view substantially undistorted in relation to the rest of the larger space.
2. Description of the Background Art
A concept of cloaking or hiding objects by making them appear invisible is known. An example of such concept is illustrated in a magician's trick involving the illusion of invisibility. In such an illusion, a first mirror is placed in front of an object to be hidden, a second mirror is placed above and away from the object to be hidden, and a third mirror is placed behind the object to be hidden. The mirrors are positioned such that light is reflected from the third mirror, to the second mirror and then to the first mirror, such that a viewer positioned in front of the first mirror would see the reflection of the object located behind the third mirror. As such, it appears to the viewer that the object has disappeared. However, such an illusion is highly limited in its practical applications, e.g., due to the need for the second mirror being hidden in a ceiling or the like. Thus, such a trick is not easily adapted to different situations or settings because the second mirror must be attached somewhere located remotely away from the object itself.
Another known example in the field of camouflaging an object to render it invisible uses a camera to capture an image the background of an object and a projector to project the captured image directly onto the object. In such a technology, a camera or several cameras are used to capture the image of the background behind an object. The object preferably is coated or covered in some type of reflective material. A projector is then used to project the image taken by the camera (and manipulated using some form of image processing), onto the object itself or onto a screen that displays the background image in front of the object to be hidden. Again, there are known disadvantages with such projection-type camouflaging. For example, the surface of the object to be hidden emits and/or reflects light such that the projection of the image may appear distorted or not lined up with the background. Further, the image being projected on the object or onto the screen is projected in two-dimensions and as such does not have the stereo-feeling/effect when seen by human eyes.
As yet another example, it is known to use carbon nanotubes to create a “mirage” type effect to hide/cloak an object. In such a technology, carbon fibers are electrically heated to very high temperatures. The extreme temperature changes of the carbon fibers cause light waves to be reflected in a field of vision. However, in order to see the “mirage” effectively, the viewing angle must be almost parallel to the objects surface. Thus, the object may not appear invisible from a straight-on view point. Moreover, while the object may not be seen by a viewer, neither is the background of the object. Instead, it appears more as if there were a mirror being placed between the object and the viewer rather that the object being invisible.
Moreover, there have been some advancements in the area of metamaterials, which are artificial materials engineered to have properties which are not found in nature. For example, in U.S. Pat. No. 8,094,378, a method is described of using metamaterials to create a hypelens or superlens that guide or bend electromagnetic waves. However, with such a method, the materials being used are not common optical materials and as such are difficult to develop and are relatively expensive.
Further, other sophisticated artificial metamaterials having a negative refractive index have been used to hide extremely small objects (similar to the size of a red blood cell) in visible light. However, materials with a negative refractive index do not occur in any natural material and the known artificially created metamaterials with a negative refractive index are only capable of cloaking a micro-object. As such, metamaterials with a negative refractive index would not be useful in any practical application for cloaking an object.
Research has also been done using plasmonic metamaterials to hide an object using microwave frequencies. However, it was only possible to cloak the object in microwave frequency. Thus, such technology would not hide an object within the visible light spectrum.
Still further, other known materials have been used to hide objects. For example, calcite crystals have been used to in conjunction with polarized light to hide an object. However, because the calcite crystals must be used in conjunction with polarized light, such a method would not work within the visible light spectrum. As another example, rare materials with a much higher refractive index, called anisotropic birefringent materials, have been used to hide a macro object in visible light within a maximum diameter of 3 mm. However, such a method is not very useful for practical applications, as such rare materials are not commonly accessible and the size of the object to be hidden is limited to below 3 mm.
Thus, while there are several known optical cloaking systems and methods, these have disadvantages and limitations associated therewith, including those briefly discussed above. Hence, a need still exists in the art for an improved, more efficient and practical optical cloaking system which functions in visible light. In particular, there is a need for such an improved, optical cloaking system involving common optical materials that can cloak an object (allowing it to appear invisible) in visible light, which is portable or easily movable but is still large enough in size to hide almost any object, which has quality with little distortion, and which can be economically manufactured.